Showing papers in "Cytologia in 1987"

Cytogenetical Studies on the Effect of Some Chlorinated Pesticides I. Effect on somatic chromosomes of Lens and Pisum

Abstract: Lens esculenta, L.culinaris, Pisum sativum and P. arvense which were included in the present study belong to one of the economically imporatnt families-Leguminosae. The somatic chromosomal anomalies were studied after root-tip (1/2, 1 and 2 hr. treatment) and seed-soak (24 hr. treatment) followed by fixation in Farme's fixative. Root-tip squashes were made in 1% acetocarmine. The used concentrations of Benzene hexachloride (BHC), Lindane and Endrin were 0.01%, 0.02%, 0.03% and 0.04% and of Aldrin and Heptachlor were 0.05%, 0.1%, 0.2% and 0.3%. A considerable fall in mitotic index was noticed from control in all treatments. The most common chromosomal abnormalities induced by these pesticides were-inactivation of spindle mechanism, condensation of chromosomes below their normal size, chromatin bridges at anaphase and telophase. Multipolar spindles were observed after BHC, Lindane and Endrin treatments. Only BHC and Lindane were found to induce C-mitosis. However, Lindane was found to be a less potent polyploidizing agent. Multinucleate cells were observed only in BHC treatments. Fragments were observed occassionally in BHC, Lindane, Endrin and Heptachlor treatments.

Effect of herbicide glean on mitosis, chromosomes and nucleic acids in Allium cepa and Vicia faba root meristems.

Abstract: The effect of various treatments of glean on mitotic activity, chromosomes and DNA amounts in the root tips of A. cepa and V. faba has been investigated. This herbicide remarkably inhibited mitotic division and depressed the DNA and RNA in the root meristems of both plants. Glean induced chromosome damage in both plants comprised of mitotic abnormalities, chromosomal aberrations and chromosomal stickiness. The effect of this herbicide on mitosis in relation to its action on DNA and RNA and on the chromosomes is discussed.

Cytogenetics of Rutaceae IV Structure and systematic significance of interphase nuclei

Abstract: The interphase nuclei of 68 species of Rutaceae representing the eight major tribes in the family were analyzed. Nuclei were classified as areticulate (two types), semi-reticulate (five types) and reticulate (one type). No eureticulate nuclei were detected. Variation of the structure among different tissues, individuals or species of the same genus was minimal and mainly associated to tissue differentiation or ploidy levels. The differences in chromatin organization among nuclear types are mainly correlated with the pattern of prophase condensation and the amount of nuclear DNA. The structure of the interphase nucleus appears to be particularly important in the cytogenetical characterization of tribes and sub-tribes of the Rutaceae. The tribe Aurantieae is the only one to be characterized by a single nuclear type (areticulate) whereas the remaining tribes show varied nuclear structure for the different subtribes. Some tribes, as Rutineae and Cusparieae, appear to have a characteristic nuclear type for each subtribe. The systematic significance of these findings is discussed.

Gamma Radiation Induced Cytological Abnormalities in Lycopersicon esculentum Mill. var. Pusa Ruby

Abstract: Healthy dry seeds of pusa ruby variety of Lycopersicon esculentum Mill. were irradiated with gamma rays at 10 KR, 20 KR, 30 KR, 40 KR and 50 KR dose levels. Meiotic studies were made in treated plants as well as in control plants. At metaphase I, meiotic abnormalities like clumping and stickiness of chromosomes, univalents, multivalents, fragments and irregular grouping of chromosomes were observed. At anaphase I, there were laggards and unequal grouping of chromosomes at poles. Germination percentage and pollen fertility were also studied. Pollen sterility seems to be the cumulative result of various abnormal meiotic stages as well as of physiological and genetic damages induced probably by breakage of chromosomes. The frequency of meiotic abnormalities with reference to the effect of radiation doses is discussed.

Cytomixis in Pollen Mother Cells of Urochloa panicoides P. Beauv. (Poaceae)

Abstract: Cytomixis was recorded during microsporogenesis in three varieties of Urochloa panicoides P. Beauv. (Poaceae) in different percentages as var. pubescens 10%, var. marathensis 12% and var. velutina 18%, while var. panicoides showed only occasional cytoplasmic connections. It was commonly observed during summer. Also, the robust plants raised in the experimental garden showed highest percentages of cytomixis. The phenomenon was more frequent in prophase I and noted upto anaphase II with decreasing frequencies. The amount of migrating chromatin was also reduced as meiosis advanced. The role of nucleolus was not clear. Cyto-logical analysis of cytomictic plants revealed the formation of upto 6% of hypo-and hyperploid meiocytes, triads, irregular tetrads and polyads.The seasonal occurrence and the intervarietal differences in the frequencies of cytomixis demonstrates that it is the expression of unbalanced genetic system of plants in response to environmental conditions. The pollen fertility and seed setting was not affected by this process indicating that the phenomenon is not of much significance.

Spontaneous occurrence of cytomixis during microsporogenesis in Almond (Prunus amygdalus Batsch) and Peach (P. persica Batsch)

Abstract: The paper records the occurrence of cytomixis in two economically important fruit species, P. amygdalus (almond) and P. persica (peach). The possible impact of the phenomenon on breeding system of the two species and the causes of its occurrence have been discussed in the paper.

A Change in Chromosome Number due to Cytomixis in an Interspecific Hybrid of Coix L

Abstract: A change in the chromosome number of some PMCs in an interspecific hybrid of Coix L. (C. gigantea×aquatica, 2n=16) through cytomixis is reported. In the cytomictic PMCs the chromosomal changes are both quantitative, having 2n=13 and 2n=17 chromosomes instead of the usual 2n=16 and qualitative, having variable number of parental chromosomes instead of the usual 10+6 gigantea and aquatica combination. Causes, places, types, consequences and nature of cytomixis are discussed. It is argued that in the PMCs, the displacement of chromatin from its nearly central position towards periphery, as if acted upon by some force and in preparation to migration, cannot be without any purpose, the latter though as yest not clear to us.

Cell volume ratios of natural and of induced tetraploid and diploid flowering plants

Abstract: Many volume ratios between tetraploid and diploid guard cells of stomata and between diploid and haploid pollen grains were compiled from the literature and from own unpublished results. The sources of possible errors are discussed. No difference was found between induced auto- and allotetraploids. Some of the ratios with tetraploids of the C0 generation, but less so of later generations, were extremely high. The medians of the ratios were highest in the C0 generation (pollen grains 2.0-2.1, guard cells 2.4) and smaller in later generations (pollen grains 1.9, guard cells 2.1). The ratios of tetraploids from nature were 1.5-1.8 and thus significantly smaller than 2. The reduction may be a result of a selection for cell size during evolution, or of a physiological self-adjustment.The length/width ratios of guard cells were on average greater, but those of anisodiametric pollen grains smaller in induced tetraploids than in diploids, with a broad range of variation. The finding for guard cells is at variance with a widely held opinion.

Genotoxicity of an Inorganic Pesticide, Copper Sulphate in Mouse in vivo Test System

Abstract: Mutagenicity of copper sulphate was evaluated in vivo by chromosome aberration, sperm abnormality and micronucleus tests in mice. Dose, route and time influenced significantly the frequency of chromosome aberration, incidence of micronucleus and sperm abnormality. Relative sensitivity of three assays are: sperm abnormality>chromosome aberration>micronuclei formation. The present results revealed the mutagenic property o CuSO4 in mouse in vivo test system.

Chromosomal Studies in the Egyptian Flora

Abstract: The first reliable chromosome counts in species of the genus Plantago L. was made by McCullagh (1934). Later more detailed cytological investigations were carried out on more than half of the species in this genus. Some of these investigations were made in connection with taxonomic studies in order to elucidate the relationships in particular groups of related species (Bocher et al. 1955, Rahn 1957, Cartier 1971, 1973, Sopova and Rizova 1975, Zemskova 1977). Other studies were concerned with investigating the cytology of Plantago species in certain floras or phytogeographic regions (Gregor 1939, Runemark 1967, Briggs 1973, Favarger and Vasudevan 1972, Fernandes and Franca 1973). The cytology of the genus Plantago in Egypt has not been a subject of a study. The chro mosome number of only three species was reported by Badr (1980). The numbers of some other species which grow in Egypt are also known from chromosome counts in plants from near floras particularly that of Europe. The present study is therefore conducted to investigate the cyto logical features in species of the genus Plantago from Egypt. This investigation deals not only with chromosome numbers but also with detailed karyotype features such as chromosome length and centromere position. The impact of karyotype features in the taxonomic relationships of the studied species is also elucidated.

Variation and Evolution on the Karyotype of Lycoris, Amaryllidaceae II. Karyotype analysis of ten taxa among which seven are native in China

Abstract: Karyotypes of ten taxa of the geuns Lycoris have been analyzed minutely. Chromosomes of Lycoris are fundamentally classified into three categories, M, T, and A type as mentioned in the previous paper (Kurita 1986). Chromosome number and formulated karyotype of each taxon are summarized in Table 13.L. aurea is highly sterile and it is supposed to be a hybrid or chromosomal mutant.In L. albiflora, a new cytorace having 2n=18 is found. Karyotype of this race consists of 5M, 1T, 11A, and lm type chromosome. The m type chromosome must be a by-product of Robertsonian fusion of two A type chromosomes. This may be a hybrid between L. traubii and L. radiata.Karyotype consisting of 3M, 5T, and 11A type chromosomes of L. cv. “lactiflora” is the flrst record in this genus. Origin of this sterile diploid plant is unknown.Other three triploid sterile taxa are also considered to be hybrids, but the exact origin of them is undecided. L. squamigera may be a hybrid between L. straminea and L. sprengeri as pointed out by Inariyama, and a parent of L. houdyshelii is supposed to be L. longituba according to its karyotype and gross morphology. The m type chromosome found in a complement of L. incarnata must be a by-product of Robertsonian fusion between two A type chromosomes of an unknown parent.

Variation and evolution in the karyotype of Lycoris, Amaryllidaceae. IV: Intraspecific variation in the karyotype of L. radiata (L'Hérit.) Herb. and the origin of this triploid species

Abstract: 1) Intraspecific variation in the karyotype of L. radiata was studied. Five hundred and nineteen bulbs from fifty-eight populations were examined.2) Standard karyotype consisting of thirty-three A type chromosomes (2n=33=33A) was found in 97.3% of examined materials.3) Standard karyotype includes two A type satellite chromosomes heterozygously. Namely the size of short arm of one satellite chromosome is smaller than that of the other. Moreover, four A type chromosomes having high r value are always included in the standard karyotype.4) In some cells, three satellite chromosomes were observed.5) Robertsonian fusion between two A type chromosomes had occurred in some bulbs, then M' and m type chromosomes were produced. So, this m type chromosome is euchromatic and it segregates normally and inherits into the daughter cells. This chromosome must be equivalent to m type chromosome observed in L. albiflora and L. incarnata.6) The karyotype consisting of 31A and 1M' was found in the bulbs from Ebira population. This M' type chromosome might also be a product of Robertsonian change between two A type chromosomes, and in this case m type chromosome or fragemented short arms were eliminated.7) Secondary constriction at the proximal region of long arm of one A type chromosome was observed in the complements of some bulbs from Uematsu population.8) The birthplace of this triploid plant is supposed to be China, and its very stable karyotype also suggests that it is a prehistoric naturalized plant introduced into Japan from China with the traffic of men.

Cytology of high alpine plants. II: Microbody activity in leaves of Ranunculus glacialis L.

Abstract: Leaves of Ranunculus glacialis, harvested at 2600 m-2800 m altitude in the Alps, contain numerous peroxisomes in close association with mitochondria and plastids. Cytochemical staining for catalase by means of the DAB-reaction is found in peroxisomes only, while staining for peroxidase is also found in the tonoplast membrane. Phloem parenchym cells in the leaves store considerable amounts of lipids. It is conceivable, that during the short growing season under stress conditions peroxisomes participate in the break-down of the energy source “lipid”.Abbreviations: DAB, 3, 3-diaminobenzidine RuBP, ribulose-1, 5-bisphosphate

Karyomorphological analysis of different species and varieties of Calathea, Maranta and Stromanthe of Marantaceae.

Abstract: Extensive analysis of morphological, anatomical and cytological characters was carried out on 14 different species and varieties of Calathea, Maranta and Stromanthe of Marantaceae. The morphological and anatomical features of these species vary between species to species and are correlated with chromosome number. These characters may serve as identifying parameters.Chromosome analysis has indicated the chromosome number to range from 2n=24 to 28 in Calathea, 2n=48 and 52 in Maranta and 2n=44 in only species of Stromanthe. The polyploid forms do not show an exact multiplication of the basic set. Duplication alongwith the minute structural alteration of chromosomes has played a role in speciation of these genera.A conspicuous variation was recorded amongst these species in length and volume of chromosomes. The length and volume did not show any direct correlation with chromosome number and a consistency in difference of these two characters was recorded as well. Differential coiling and uncoiling of the arm and ratios of different chemical components in the chromosome structure, have been suggested as responsible for this difference. The similarities in gross karyotype and morphological characters indicate a close relationship between these genera.

Light and Electron Microscopic Observations of Mitochondrial Fusion in Plasmodia Induced Sporulation in Physarum polycephalum

Abstract: The morphological behavior of cell nuclei, mitochondria and mitochondrial nuclei during sporulation in Physarum polycephalum was investigated using light and electron microscopy. The plasmodia which reactivated from sclerotia on non-nutrient agar plates preferentially entered into sporulation. A night vision camera and time lapse VTR were available to monitor morphological changes and determine the exact time course. Sporulation processes were classified into six stages, by morphological characteristics. The initial event of sporulation was characterized by the formation of many protoplasmic knobs along plasmodium strands (protoplasmic balling stage). A papilla was projected from the apical region of each protoplasmic knob, elongated and changed to form a stalk (stalk elongation stage). The apical part of the stalk then began to expand until it reached a maximum point of stalk elongation, thereafter differentiating into the head of the sporangium (head expanding stage). After a stage without morphological changes (resting stage), the color of the sporangial head gradually changed from pale yellow to black (head blackening stage). After full blackening of the sporangial head, sporangia were completed (mature stage). 4'6-diamidino-2-phenylindole (DAPI) epifluorescence microspectrophotometry showed that the cell nuclear DNA content in sclerotia and starved plasmodia before the resting stage was the same as that in somatic diploid G2 phase nuclei. Only a single somatic nuclear division occurred at mid-resting stage. Meiotic DNA synthesis then occurred during the late resting and head blackening stages, when cytoplasmic cleavages occurred. After DNA synthesis, cell nuclei persisted in a long G2 phase of about one day and stopped at meiotic prophase I. In sclerotia and starved plasmodia, mitochondria were spherical or oval and contained one electron-dense mitochondrial nucleus (mtnucleus). Mitochondria and mt-nucleus became smaller in size in starved plasmodia. The DNA content per mitochondrial nucleus at that time was reduced by half as compared with that at the early starved plasmodium stage. Dumbbell-shaped mitochondria appeared during the resting stage; these had two mt-nuclei, each located discretely at either side of the dumbbell-shaped mitochondrion. Mitochondria containing 3-6 nuclei were also observed, at low frequency; multinucleated mitochondria persisted up to meiotic prophase I. The mitochondria in amoebae which originated from spores contained only one mt-nucleus. These results indicate that mitochondrial nuclear fusion occurs at some stage between spore germination and the amoeba stage, following mitochondrial fusion at the resting stage of sporulation in Physarum polycephalum.

Cytophotometric Estimation of Nuclear DNA in Different Species and Varieties of Agave

Abstract: A detailed cytological and cytochemical investigation involving determination of somatic chromosome number, karyotype, total chromosome length, volume and estimation of 4C nuclear DNA were carried out in 9 different species and varieties of Agave. Of the nine species studied, five belonged to diploid level with 2n=60 chromosomes and the rest were triploid, tetraploid, pentaploid and hexaploid having 2n=90, 120, 150 and 180 chromosomes respectively. Inspite of a distinct bimodal karyotype with very long and very short chromosomes in the 5: 25 ratio and a constant base number of n=30 chromosomes featured in the detailed karyotype analysis, each species has got its own distinct karyotype, differing from the rest in minute details. The total chromosome lengths and volumes differed both within and outside the same ploidy level and the volume did not necessarily increase with the increase in chromosome number.The amount of 4C nuclear DNA, estimated through Feulgen microspectrophotometry and expressed in arbitrary unit of relative absorbances, did not show much variations in the diploid species, while the triploid species revealed slightly lesser value than that of one specific diploid species. The difference in the amounts of nuclear DNA was insignificant amongst the pentaploid and hexaploid species as compared to the difference of their chromosome numbers. No direct correlation could, however, be established between the cytological parameters and the amounts of nuclear DNA. On the basis of overall analysis, the influence of structural alterations in affecting the amounts of nuclear DNA as well as other cytological characters from diploid to hexaploid level has been suggested.

Cytoskeleton, Microtubules, Tubulin and Colchicine: a Review

Abstract: Cytoskeleton: Its chemical and physical organization Cytoskeleton was first visualized as fluorescence shape reflecting the distributions within non-muscle cells of subunit proteins forming filamentous subcellular structures , which is a network with associated nucleus (Lazarides and Weber 1974, Weber and Groeschel-Stewart 1974, Weber et al. 1975). Therefore this structure has been known as a fibrous and contractile skeleton of cells. Proceeding studies on different kinds of cells increased the number of protein subunits associated with cytoskeletons more of which belong to the filamentous struc tures and its connections (Satir 1984, Weber and Osborn 1982). However, cytoskeleton is described in a broad sense the three dimensional network formed by the nucleus, organelles, fibrous systems and membranes (Weber and Osborn 1982). Since the data concerning the proteinous organization of fibrous part of cytoskeleton had already been cited, in this article evidences concerning other mentioned aspects of cytoskeletal organi zation will be presented. Cellular proteins that constitute cytoskeletal filaments are not specific for these substruc tures. Even they are contained in cellular membranes and nucleus (Douvas et al. 1975, Gruenstein et al. 1975, Burridge and Phillips 1975, Blitz and Fine 1974, Bhattacharyya and Wolff 1975). Recent reports expand these findings and lead to the concept that cytoskeleton and remaining part of cells share similar protein components (Carraway et al. 1982, Nakayasu and Ueda 1983, Hubbard and Ma 1983, Rotman et al. 1982, Phillips et al. 1980, Lehto 1983, Wilkins and Lin 1981, Armbruster et al. 1983). Morphological studies showed that cytoskeletal systems are associated with ribosomes (Wolosewick and Porter 1976, Lenk et al. 1977, Fulton et al. 1980, Cervera et al. 1981, Jeffery 1982). Myofibrils that are analogue to cytoskeleton in muscle cell are associated with ribonucleic acids and contain phospholipids (Zak et al. 1967, Ozgunes and Artvinli 1982). Besides phospholipids, other components that assemble to membranes also retained in Triton X-100 extracted cells which comprise cytoskele tons (Schick et al. 1983, Nagai and Sakakibara 1982, Ben-Ze'ev and Abulafia 1983, Wheeler et al. 1984, Carraway et al. 1983, Moss 1983). In detergent-treated cytoskeletal residues, some receptor and enzyme activities tested could also be detected (Prives et al. 1982, Streuli et al. 1981, Sahyoun et al. 1981, Tuszynski et al. 1984, Tashiro and Ishizaki 1982). Sphingolipids and creatine phosphokinase activity in cytoskeletons of intact cells were showed by immuno flourescence microscopy (Sakakibara et al. 1981, Eckert et al. 1980). In addition to the data that reveal contribution of membranous components to cyto skeletal organization, those that and surface membrane were reported (Nicolson 1976). Sub sequently, the presence of such associations were observed (Koch and Smith 1978, Lehto et al. 1983, Williams et al. 1979, Ash and Singer 1976, Ash et al. 1977, Flanagan and Koch 1978).

Karyotypes and chromosome morphology in the genus Mikania (Compositae). I

Abstract: Karyotypes from six species of genus Mikania were studied utilizing root tip metaphase mitoses. Two species were diploid with 2n=36, M. cordifolia was diploid with 2n=34, M. laevigata, was diploid with 2n=38, M. micrantha and M. viminea were tetraploid with 2n=72 and 2n=68, respectively. Five out of the six species analysed had one pair of a comparatively long chromosome with a secondary constriction in the long arms, and one species (M. micrantha) had two pairs of such long chromosomes. The basic chromosome number of this genus is 18, and we suggest that there is an evolutionary trend towards formation of aneuploid series and polyploidy.

Contributions to the Cytological Effects of Medicinal Plants

Abstract: This work has demonstrated that water extracts of the two medicinal plants, Boerhaavia diffusa (Fam. Nytaginaceae) and Vernonia amygdalina (Fam. Compositae) contain active substances which are mitodepressive in Allium cepa. The major observable effects are decrease in the number of dividing cells and changes in chromosome structure leading to stickiness. Higher concentrations of the extract from V. amygdalina lead to nuclear disintegration and cell death and this is believed to be due to the presence of the sesquiterpene lactones, vernodalin and vernomygdin.

Isolation of chromosomes from cell suspension cultures of Vicia hajastana.

Abstract: The chromosomes of Vicia hajastana were isolated from partially synchronized cell cultures. Treatment of cells with hydroxyurea (5mM) for 24h followed by colchicine (0.01%) for 16h induced the maximal frequency of mitotic synchrony.The procedure for metaphase chromosome isolation involved lysis of cells with partially digested cell walls in citrate-phosphate buffer (pH 3.0) and the separation of the released chromosomes by filtration through polycarbonate filters. Isolated chromosomes retained a morphology comparable to that observed in the intact cells.

Effects of Luffa operculata on Allium cepa Root-tip Cells

Abstract: Allium cepa root-tip cells submitted to infusions of Luffa operculata dried fruit showed decreased mitotic index, polyploid nuclei and metaphase-C, suggesting a possible interference of the plant with the mechanism of formation of the mitotic spindle.

Cytotaxonomical Studies of South Indian Scrophulariaceae

Abstract: The chromosome number of 21 species belonging to 17 genera of Scrophulariaceae from South India has been studied, of which first record of chromosome has been made in Lymnophila heterophylla, Moniera cuneifolia, Ilysanthes tenuifolia, I. oppositifolia, Micrargeria wightii and Sopulia trfda. Chromosome numbers determined in the present study range from 2n=12 to 20=80.Chromsome numbers determined in the present study and those reported previously in the family (Fedorov 1974) reveal the presence of a continuous series of basic number between n=6 to 84. The commonest basic number in the famly is n=8 and it is assumed to be the original basic number of the family. It appears that aneuploid changes of chromosome numbers produced the basic numbers of n=6, 7, 8, 9, 10, 11, 12, 13 and 14 in the early evolution of the family, after which polyploid and dibasic amphidiploid gave rise to the higher basic numbers (n=17 to n=84) now found in the family.Karyotypes in the family also show differences in absolute chromosome size indicating changes in nuclear DNA in evolution. The meiotic chromosome number studied in 17 species is in confirmation with the mitotic chromosomes. The presence of mutivalents and quadrivalents along with bivalents and the presence of anaphasic laggards and bridges and triplar anaphases show evidences in support of the aneuploid and polyploid nature of the species.

Cytogenetical investigations in Rutaceae. II: Meiotic studies in three intergeneric hybrids of Citrus

Abstract: Meiotic studies were conducted in two Citrus-Poncirus and one Citrus-Fortunella intergeneric hybrids. Regular bivalent formation and equal distribution of chromsomes at different stages of meiosis indicated similarity between the genomes of Citrus-Poncirus and Citrus-Fortunella. Cytomixis and secondary association of bivalents indicated a hybrid and polyploid nature of these genera. The basic chromosome number of Citrus and allied genera was reconfirmed as n=3.

Karyomorphological Studies in South Indian Rubiaceae

Abstract: The chromosome number of 41 species belonging to 24 genera of Rubiaceae from South India has been studied. The chromosome numbers range from 2n=18 to 2n=72. First record of chromosome numbers have been made as many as 11 species and deviant records of chromosome number as against the previous reports have been worked out in 2 species. In the rest of the species studied, the present report of chromosome numbers confirms the previous records.A common survey of the chromosome numbers in Rubiaceae reveals the existence of graded series of haploid numbers from 6 to 110. Of those, haploid numbers n=11 and n=22 represented the highest frequency among the taxa studied. Therefore, it may be assumed that the original primary basic number may be 11 and it should have given rise to derived primary basic number 22. A process of chromosomal reduction as observed among the species of Crepis might have been in operation so that the basic number 11 might have got reduced to n=10, n=9 and finally to n=6 by a series of unequal translocations involving concurrent loss of inert heterochromatin parts of the chromosomes. The other higher haploid numbers above the level of n=11 should have been arisen by means of aneuploidy and euploidy.As revealed by karyotype analyses of 41 taxa of Rubiaceae studied it is clear that, there is a close correlation between the size and the number of somatic chromosomes. Karyotypes in Rubiaceae also show differences in absolute chromosome size indicating changes in nuclear DNA in evolution. No definite trend of either phylogenetic increase or decrease of chromosome size is indicated by the available limited data.In the present study, critical karyotype analyses of as many as 41 species of Rubiaceae showed asymmetrical karyotype. Along side this advanced character, and by the common occurrence of subterminal kinetochores showed that this family may be considered as one of the most highly evolved families of Angiosperms.

Relevance of chromosome number variation to yield and quality of essential oil in Mentha arvensis L.

Abstract: Six morphologically distinct genotypes of Mentha arvensis L. consisting of four clones introduced from Japan (CIMAP/MA-2), Thailand (CIMAP/MA-3), Taiwan (CIMAP/MA-4) and Brazil (CIMAP/MA-5) and two bud-sports (CIMAP/MAS-1 and CIMAP/MAS-2) of a Thailand clone (CIMAP/MA-3) were studied under uniform environmental conditions for somatic chromosome numbers, yielding ability and essential oil quality. The somatic chromosome number in these genotypes ranged from 2n=64 to 108. Three clones viz. CIMAP/MA-2 (2n=84), CIMAP/MA-5 (2n=72) and CIMAP/MAS-2 (2n=108) possessed chromosome numbers multiple of the base number (x=12) while the remaining three clones (CIMAP/MA-3, CIMAP/MA-4 and CIMAP/MAS-1) contained aneuploid numbers such as 2n=98, 64 and 90, respectively. The results on chromosome number variation in the two bud-sports-CIMAP/MAS-1 (2n=90) and CIMAP/MAS-2 (2n=108) suggested that these two cytotypes might have originated by addition or reduction of chromosomes due to irregular mitosis in the bud meristem of the parental clone-CIMAP/MA-3 with 2n=98. It is likely that a similar mechanism for reduction of chromosome number from 2n=96 to 2n=84 might have operated in CIMAP/MA-2. The relevance of a large variation in chromosome number brought about by introgression and sporting and its subsequent fixation through vegetative propagation in evolving the observed cytotypes in M. arvensis is discussed. The variation among the six genotypes for various characters like plant height, leaf/stem ratio, fresh herbage yield, oil content, oil yield, oil composition and congealing point of oil indicated a genotypic control for these traits. CIMAP/MAS-1 and CIMAP/MAS-2 with significantly high oil content, oil yeild and exceptionally greater amount of menthol in the oil proved significantly superior over rest of the genotypes. The absence of menthyl acetate in the oil of CIMAP/MAS-1 and CIMAP/MAS-2 quite contrary to the remaining four clones is interpreted in the sence that these two genotypes might be in possession of homozygous recessive gene ‘e’ responsible for completely blocking the conversion of menthol to menthyl acetate.

Meiotic abnormalities induced by dye industry waste water in Chlorophytum amaniense Engler

Abstract: Treatment of flower buds of Chlorophytum amaniense with different concentrations of dye industry waste water resulted in the production of high percentage of abonormal PMCs. The abnormalities observed included stickiness of chromosomes, laggards, bridges, fragments and micronulcei. The higher frequency of stickiness observed is apparently responsible for some of the above abnormalities. It is concluded that dye industry waste water with rich amounts of heavy metals act as potential mutagens.

Effects of Urea on Mitotic Chromosomes of Mice and Onion

Abstract: Urea, a common fertilizer used to supplement soil with nitrogen, has been found to cause a seven times increase in the incidence of chromosomal abnormalities like breaks, clumping, pulverisation and polyploidy in albino swiss mice fed with a 500 mg dose for 5 days. The breaks were non-random in their distribution-more common in larger chromosomes, and the middle and distal regions of the chromosomes. The agrochemical could act as a mito-inhibitor (by 21.05% decrease) in onion root-tip cells, where fragmentation of chromosomes was found to be the most common among the abnormalities induced (0.06% in control, 0.80% in treated).

Nuclear DNA Variation in Relation to Cytological Features of Some Species in the Genus Plantago L

Abstract: The nuclear DNA content in 14 taxa belonging to 9 species of Plantago from Egypt has been measured using cytophotometric methods. The recorded DNA amounts were related to the karyotype features of the studied species. In general the amount of nuclear DNA/genome is correlated with the basic chromosome number. Species having x=6 i.e. P. lagopus, P. lanceolata, P. major and P. notata contain higher amounts of nuclear DNA/genome when compared with the species having x=5 i.e. P. albicans, P. crassifolia, P. crypsoides and P. cylindrica. Three samples of P. ovata (x=4) were found to contain the least amounts of DNA/genome. It was also found that polyploid taxa contain higher amounts of 4C DNA/nucleus than diploid species. The impact of these results on the taxonomic relationships of the studied species is discussed.

Nuclear changes and organogenesis during callus culture of Urginea indica Kunth., Indian squill

Abstract: Cytological analyses were carried out to follow the nuclear events occurring during growth and differentiation of calli derived from bulb scale explants of diploid Indian squill, Urginea indica Kunth. Although bulb scale explants had a negligible level of DNA variation, the dedifferentiating calli exhibited a large variation. The meristemoids consisted of predominantly diploid cells whereas dedifferentiating calli were highly polyploid. Regeneration occurred in 8-10 week old calli but not in older cultures. Fragmentation amitosis, multiplolarity, binucleate cells etc. were characteristic of older cultures but were not noted during induction of calli despite 2, 4-D being used for establishing cultures. Regenerated plants were predominantly diploid.